My 97 gsx has minimal upgrades. I’ve installed hard intercooler piping, injen intake and have a 3” cat back. I finally installed an aftermarket boost gauge and here’s the issues I’m having. Even before the boost gauge install. My car stumbles on boost and when I get boost then I smell exhaust fumes after I left off the gas. And according to my boost gauge I’m only hitting 9psi at full boost. My oxygen sensor bank 1 is throwing a code as well. How do I check for boost leak? Do I just start up the car and spray the vacuum lines and intercooler piping down with soapy water or what? And what could be causing my issues?

Also to add. I did the waste gauge restricor removal for extra boost. I know stock boost is 12psi